Quasi four-level solid-state lasers operating in the 2 .mu.m wavelength region are used for sensing wind velocity, as optical pumps for mid-infrared parametric oscillators, for remote sensing of water vapor or carbon dioxide, for medical applications such as laser angioplasty, for material processing applications, and for communications.
In general, quasi four-level lasers operating in the 2 .mu.m wavelength region utilize laser material made from a host material doped with laser active ions from the group of rare earth ions such as holmium (Ho) and thulium (Tm), transition metal ions such as chromium (Cr) or combinations thereof. The host materials for such lasers come from the group of crystals such as YAG, YLF, YSGG, GSGG, GSAG, YSAG, YAlO, GGG, YGG and LLGG. As is known in the art, the Ho:Tm:Cr:YAG laser has provided the best performance for flashlamp-pumped, quasi four-level lasers operating at room temperature. However, Ho:Tm:Cr:YAG laser has a high threshold and further suffers from upconversion losses. While performance improvements can be achieved by lowering the laser's operating temperature, the addition of cooling devices adds to the complexity and cost of the laser.